We propose the establishment of an Environmental Health Research Center whose main purposes are 1) to study the effects of environmental exposures on humans, and 2) to determine host factors (genetic and other) influencing response to these exposures. To accomplish these goals we bring together an interdisciplinary team of investigators from three major Southern California universities; USC, UCLA and Cal Tech. The research of our Center will rely on several interdisciplinary cornerstones: detailed exposure assessment, including toxicokinetics and biomarkers; cutting edge study design, including the most powerful statistical and epidemiologic approaches; and the basic sciences, including physiology, molecular biology, genetics, chemistry and engineering. The foci of the proposed Center cover a wide range of problems and address environmental exposures of public health importance including air pollution, magnetic fields, pesticides, organic compounds, aflatoxins, radon, passive smoking, bioaerosols and nitrites. The 6 Research Cores consist of: Respiratory Effects of Environmental Exposures; Exposure Assessment; Environmental Exposure and Childhood Cancer; Study Design, Epidemiology and Statistical Methodology, Neuropsychiatric Diseases, and Environmental Exposures and Adult Cancer. The 4 Service Cores consist of Molecular Biology Services Core, Analytic Chemistry, Exposure Assessment and Aerosol Sciences Core; Biological Sample Processing and Sample Service Core; and Biostatistics Service Core. The Center administration will further efforts to involve more investigators in Center related research and will set up a series of activities planned for enrichment and for community outreach and education. A pilot fund program will be established to attract new investigators and new research projects. Because we have a critical mass of investigators, a history of excellence, an established and deep commitment to environmental health problems a belief in interdisciplinary research, and a rich array of resources, we believe the time is right to establish an NIEHS Research Center in Southern California. Such a Center would maximize efficiency, would spark new research and would create opportunities for new research involvement from other members of our research communities.